Answer:
13.5 ms
Step-by-step explanation:
The sound wave travels with uniform motion in both cases, so the time taken to cover a distance d is given by:

where
d is the distance to cover
v = 340 m/s is the speed of sound in air
So for the people across the newsroom,
d = 4.7 m
So the time taken is

The radio waves instead travels with uniform motion at the speed of light:

So the time taken for them is

where
d = 82 km = 82,000 m
is the distance of the people who are 82 km away. Substituting,

Therefore, the difference in time is
